AT510313A1 - METHOD FOR INCREASING THE INTRUSION DEPTH OF A OXYGEN BEAM - Google Patents

Description

1 201009394

description

Name of the invention

Method for increasing the penetration depth of an oxygen jet

Field of engineering

The invention relates to a method for increasing the penetration depth of a volume flow and a mass flow in the bed of a

Crude iron generating units entering oxygen jet of technically pure oxygen for the gasification of carbon carriers present in the bed.

State of the art

In the production of pig iron in one

A pig iron production unit such as a blast furnace or a smelting reduction agglomerate such as a melter gasifier used in the method COREX® or FINEX ©, a reducing gas is obtained by gasification of carbon carriers by blowing a hot blast or oxygen jet. Oxidizing iron carriers are reduced by means of this reducing gas, and subsequently the resulting reduced material is melted into pig iron.

In the case of the melter gasifiers used in the COREX® and FINEX® processes, oxygen nozzles are installed at the circumference of the melter gasifier between the hearth and the charbette of the melter gasifier in order to ensure that the oxygen for the gasification of carbon for the production of the reducing gas and the energy required for melting the iron carriers are as uniform as possible Scope of the

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Blow molten carburetor into the bed of the melter gasifier. When the iron carriers melt, liquid pig iron and liquid slag are produced. The hearth here is the region of the melter gasifier below the oxygen nozzles, in which there is no flow through the reducing gas. In the stove are liquid pig iron, liquid slag and part of the char. Char refers to thermally degassed carbon carriers. As Charbett while the area is referred to in the melter gasifier, which is above the oxygen nozzles; In addition to liquid pig iron, liquid slag and char, it also contains unmelted and partially reduced iron carriers and additives. The charbet is flowed through by the reducing gas, which is formed by reacting the introduced oxygen. The oxygen streams entering the melter gasifier through the oxygen nozzles form the so-called race-way in the interior of the melter gasifier, in which gasification of carbon carriers already takes place, reducing gas already being produced. Race-way is understood to mean the vortex zone in front of the oxygen nozzles, in which the reducing gas is formed from oxygen and carbon carriers. The term vortex zone reflects the highly turbulent fluidized bed-like flow conditions in the area of the raceway. The incoming oxygen jet creates a cavern in the bed of the charbette. The cavern is formed by the momentum of the incoming oxygen jet and by the gasification reaction of the oxygen with the char. The area of the cavern is called Race-way. The Race-way has compared to the Charbett, which is a fluidized bed, a much higher degree of void. The raceway extends according to the arrangement of the oxygen nozzles on the periphery of the melter gasifier in the interior of the melter gasifier in a horizontal plane. The cross-sectional area formed when viewed from above by the length of the race-way ···. : ::: - :: · * ·· ». ·· * · ». Is also referred to as an active ring surface, wherein in the term active ring surface actively refers to the fact that drainage of liquid pig iron and liquid slag particularly well due to the degree of void of the raceway the race way, and that resulting from gasification of carbon carriers reducing gas from the raceway enters the Charbett. The width of the active ring surface is determined by the length extension of the raceway, and thus by the penetration depth of the oxygen jet.

Even with a blast furnace, in which hot air or oxygen is injected through corresponding nozzles distributed around the circumference of the blast furnace, also referred to as wind forms, race ways with an active ring surface are formed in the region of the nozzles. For the Charbett a melter gasifier results in the usual use of an oxygen jet of technically pure oxygen having a temperature between -15 ° C and + 45 ° C, and due to the compared with hot blast furnace operated smaller diameter of the oxygen nozzles used, compared to the fixed bed present in a blast furnace operated with hot blast, a significantly lower penetration depth of the oxygen jet into the bed. This results from the shorter or narrower race way in Charbett compared to a hot blast furnace operated comparatively small active ring area at the periphery of the melter gasifier, whereby the gas permeability for reducing gas in the Charbett or the drainage of liquid pig iron and liquid slag in the Stove are comparatively worse. Furthermore, compared to coke-operated blast furnaces, the use of charcoal and / or coal briquettes as carbon carriers reduces Charmatrix's hydraulic diameter in a melter gasifier, thus making it more difficult to drain molten iron and liquid, especially highly viscous, slag. which can lead to disturbances due to backflow of liquid pig iron and / or liquid slag in front of the oxygen nozzles.

An increase in the depth of penetration of the oxygen jet into the bed would significantly increase the active area in an oxygen-operated blast furnace as well as in a melter gasifier and thus improve the outflow of liquid pig iron and of liquid slag.

The reducing gas flows substantially upwards. Seen in the flow direction of the reducing gas after the race way, ie above the raceway, it comes in the bed of a melter gasifier or blast furnace to undesirable fluidized areas, also called bubble or channel formation. In these areas, a quantity of gas enters the bed of solids under high pressure, and the resulting mixture of solids and gas behaves like a fluid. The formation of fluidized regions is undesirable because they can lead to so-called blow-throughs through the bed of the melter gasifier or blast furnace. Blowers result in sudden increases in gas flow, dust levels, and composition of gas discharged from the melter gasifier or blast furnace, making the operation of such units less manageable. Furthermore, in blow-by particles are discharged from the melter gasifier or blast furnace in lines for the discharge of reducing gas or blast furnace gas.

In addition, fluidized areas are undesirable because optimal phase control of gas and solid is hindered by them. In fluidized areas, a mixture of material from the upper and from the lower part of the Charbettes can come - so passes, for example, iron oxide from the upper part of the Charbettes in the

At the bottom of the charbette, finely reduced and partially molten iron from the lower part of the charbette is transported to its upper part.

When introducing a larger amount of gas, especially a larger amount of oxygen in the bed, with melter gasifier and blast furnaces operated with oxygen, increases the risk of the formation of fluidized areas with a constant penetration depth.

If the depth of penetration of the oxygen jet is increased compared to a ground state, a certain amount of gas can escape from the race way into the bed via an area which is larger in comparison to the ground state. Accordingly, pressurized conditions in the vicinity of the oxygen nozzles leading to the formation of fluidized regions will be less spatially and temporally less frequent in the vicinity of the oxygen nozzles, and as a result, fluidized regions in the vicinity of the oxygen nozzles will be less large and less abundant.

In a melter gasifier is in the range of the entry of the oxygen jet in the bed, so the race-way, due to the high flow rate - which is many times higher compared to a blast furnace, the chemical and thermal volume expansion, and due to the smaller Char size compared to the mean size of the coke in the blast furnace, a vortex zone before. According to known laws practically no increase in the penetration depth is achieved by higher flow velocity of the oxygen jet. Increasing the flow rate of the oxygen jet would increase the mechanical stress on the char. The mechanical stress would be due to momentum transfer between the particles of the oxygen beam and the components of the Charbette - so the Char - and in the following by 6 201009394

Increase momentum transfer between the components of the charbette with each other. As a result of the abrasion or decay of the character caused by the momentum transfer or the mechanical stress caused thereby, more fine grain would be formed in the vortex zone. For the decay of the char, the specific momentum transmitted per unit area is the determining quantity. The characteristic for this is the impulse force, which represents the specific impulse per unit area.

However, more fines in the vortex zone results in a reduction in the hydraulic diameter of the raceway's vortex zone, which in turn degrades the drainage of liquid pig iron and liquid slag through the active annulus.

In the case of a fixed bed in a blast furnace, an increase in the penetration depth can be achieved by increasing the oxygen velocity.

There is a significant difference between a hot blast furnace and a blast furnace operated with oxygen. The penetration depth of the

Oxygen jet is significantly lower in a blast furnace operated with oxygen compared to the penetration depth of hot blast in a hot blast furnace of the same power. This is because the mass flow of introduced gas in the oxygen flow is lower because not as in the hot air along with the required amount of oxygen, a large amount of nitrogen is introduced. In the case of a blast furnace operated with oxygen would have to achieve a penetration, which is present in a hot blast furnace of the same power, the

Oxygen velocity compared to the speed of the hot blast are increased - it would, however, as described above, to increased mechanical destruction of f ·· · · «* * *« «···« «* * | * * * * I · · · 201009394 7

Coke in the blast furnace due to momentum transfer and accordingly by fine grain formation to a lower gas permeability of the fixed bed in the blast furnace.

Summary of the invention

Technical task

The object of the present invention is to provide a method for introducing an oxygen jet into the bed of a pig iron production unit, in which the abovementioned disadvantages are avoided.

Technical solution

This object is achieved by a method for increasing the penetration depth of a with a volume flow and a mass flow in the bed of a pig iron generator, entering oxygen jet of technically pure oxygen for gasification of existing in the bed carbon f Trägä, characterized in that the ratio volumetric flow to mass flow of the oxygen beam is increased.

Technically pure oxygen has an oxygen content of at least 85% by volume, more preferably at least 90% by volume.

Preferably, the pig iron production unit is a smelting reduction unit such as a melter gasifier or an oxygen blast furnace. «Φ · * · · * # · ft«

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Advantageous Effects of the Invention

The penetration depth is increased by increasing the volume flow to mass flow ratio.

Mass flow and volumetric flow refer to a given operating condition; So it means mass flow and volumetric flow at the prevailing pressure and temperature conditions in the given operating condition.

By increasing the penetration depth of the oxygen jet into the bed, the active ring area of the melter gasifier is increased. Thus, there is a lower flow rate of reducing gas as it flows up through the charbet. On the one hand, a typical, but undesirable, bubbling formation typical for fluidized beds present in a melter gasifier is reduced, and on the other hand, the heat and mass transfer between the reducing gas and the bed in the melter gasifier is improved.

The area available for the drainage of liquid pig iron and liquid slag is increased, thus reducing critical backflow of these liquids for the oxygen nozzles used to introduce the oxygen jet into the melter gasifier. In addition, due to the inventive increase in the penetration depth of the oxygen jet better metallurgical conditions in the stove - for example, better phase exchange between solid and liquid phases of slag and pig iron - and compared to a lower penetration depth improved Abstichbedingungen -es occur less disturbances in the tapping process.

Preferably, the volume flow is increased while the mass flow is constant. • * • · > ·· * «* Φ Φ · · · β · 201009394 9

In this case, a constant amount of oxygen is introduced into the bed per unit time.

Constant mass flow is to be understood in the plant 5 sense and also includes the regulation by a given operating condition - such as by given melting performance, heat demand, type of raw materials used, pressure, temperature determined - occurring fluctuations of up to +/- 10 % of the value desired at a given operating condition.

The oxygen jet enters the bed at a flow rate.

According to one embodiment of the method 15 according to the invention, the temperature of the oxygen jet is increased.

Increasing the temperature increases the volume flow to mass flow ratio.

Advantageously, by the associated entry of energy into the pig iron production unit 20 kind of energy input, for example via

Fuel addition in the pig iron production unit can be saved.

According to a further embodiment of the method according to the invention, the temperature of the oxygen jet is increased at a constant flow rate.

This is to be understood as the constant flow velocity in the plant-technical sense and also includes the fluctuations occurring by regulation to a given operating state of up to +/- 10% of the value which is desired for a given operating state.

By the measure, the flow rate 35 to obtain consistent, the 10 201009394

Flow rate-based pulse of the oxygen jet kept constant. With an increased penetration depth and entry surface, the impulse force is then reduced. As a result, correspondingly less fine grain is formed.

In order to ensure a constant mass flow at a constant compared to the starting temperature of the oxygen jet at a constant flow rate, although with an increase in the temperature, the density of the oxygen beam decreases, the diameter of the oxygen nozzle to be used at the elevated temperature is made correspondingly larger.

Furthermore, it is recommended to isolate the oxygen nozzles inside or to isolate the oxygen supply to the oxygen nozzles and / or run so that the heat losses are low.

To increase the temperature of the oxygen jet, it is preheated before it enters the bed of the pig iron production unit.

This can be done by means of a single or several of the following methods in combination: - combustion of a solid, liquid or gaseous fuel - for example, from the process of pig iron production, in which the pig iron production unit is used, resulting process gases such as top gas from a reduction shaft; For example, natural gas - with oxygen through a burner, and mixing the resulting hot gas with the oxygen.

Preferably, in this case, the mixing takes place with the oxygen in the combustion chamber of the burner to minimize the influence of temperature on the lining of the oxygen-carrying lines. Mixing oxygen with steam and / or hot nitrogen in the mixing chamber or at the injection point - Use of indirect heat exchangers, for example - with preheating using waste heat from COREX © / FINEX © process gases, - at Preheating by steam, - under preheating by other heat transfer media such as thermal oil or nitrogen, - under preheating hot flue gases from the combustion of fuels. This can also take place, for example, via hot flue gases from existing installations such as, for example, coal drying plants, reduction gas furnaces, power plants.

In the case of preheating by steam, it is possible, for example, to use condensation or counterpressure steam heat exchangers. In any case, the steam sources must have a high availability.

Supply of heated oxygen can be made directly from the oxygen production plant used for its supply. It can also be used in an oxygen production plant resulting warm oxygen, with or without additional heating. According to an embodiment variant according to the invention, the oxygen in the oxygen production plant is heated by indirect heat exchange of the oxygen with hot process air of the oxygen production process. According to another embodiment, the oxygen is heated by adiabatic compression of gaseous oxygen.

The heating of oxygen can also be done in two stages, for example by first preheating to, for example, 100 -150 ° C at low oxygen pressure, and in further episodes an adiabatic compression to about 300 ° C is performed. 12 201009394

The preheating of the oxygen can be done according to a further embodiment of the method according to the invention by means of preheating of oxygen by means of a plasma torch and mixing with not so preheated oxygen.

It is preferred to heat the oxygen by waste heat of the oxygen production plant and / or by waste heat of a power plant.

As an oxygen production plant is meant primarily an Air Separation Unit ASU. In such an ASU are a variety of compressors such as Main Air Compressor MAC, Booster Air Compressor (BAC) available. Combined Cylce Power Plants in particular feature gas turbines that are coupled with aircompensators.

Downstream of such compressors in air generators or power plants is compressed gas heated by compression, the heat of which is dissipated as waste heat to the environment. This waste heat is preferably used to heat the oxygen, which is introduced into the fixed bed of a melter gasifier. Increasing the temperature of the oxygen jet results in a reduced need for carbon carriers to provide the energy required to melt the iron carriers. This will make the process of pig iron production more cost effective and reduce specific emissions, especially of CO2, in pig iron production.

The oxygen jet enters the bed at an inlet pressure chosen to overcome the pressure loss occurring during the flow of the reducing gas formed during the reaction of the oxygen over the charbette to the settling space. 201009394 • *

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According to one embodiment of the method according to the invention, the inlet pressure is reduced while maintaining the mass flow. In order to be able to continue to run the process of pig iron production, for example, while the pressure in the calming room is lowered or the Charbett reduced in order to reduce the pressure loss. By reducing the inlet pressure, a higher volumetric flow can be achieved with a constant mass flow. Constant mass flow is to be understood in terms of plant technology and also includes the fluctuations occurring by regulation to a given operating state of up to + / - 10 x% of the value that is desired for a given operating condition.

In order to ensure a constant mass flow at a reduced compared to an initial value inlet pressure of the oxygen jet, although with a reduction in pressure, the density of the oxygen jet decreases, the diameter of the oxygen nozzle to be used at the reduced pressure is made correspondingly larger.

Preferably, the temperature of the oxygen jet entering the bed is at least 200 ° C, preferably at least 250 ° C.

The flow rate of the oxygen jet entering the bed is preferably in the range from 100 m / s to the speed of sound, preferably in the range from 150 to 300 m / s. Here, the speed of sound under the pressure / temperature conditions of the oxygen at the entrance is meant.

Under 100 m / s risk there is a great risk of nozzle damage due to backflow of molten pig iron into the nozzles. From the speed of sound there is a high pressure loss over the oxygen nozzles and high energy requirement * t I · · · f * ·· · * * * * ************************************************ to build up the pressure necessary for such a speed. In addition, the large momentum of the oxygen jet associated with such high velocities greatly contributes to undesirable fine grain formation.

According to an advantageous embodiment of the method according to the invention is carried out together with the oxygen jet injection of carbon carriers in solid or liquid or gaseous form, for example coal / oil / gas, in the oxygen jet before, formed in the region of the entry of the oxygen jet into the bed, Race way and / or in the race way.

In this case, the effect is achieved by gasification of these carbon carriers effectively a larger gas volume in the race-way is formed and introduced into the bed, as if only the oxygen flow enters the bed - because the introduced gas volume is composed of the incoming oxygen jet and at Gas resulting from the gasification - called resulting gas jet. With the same amount of oxygen entering the bed, an increase in the ratio of the volume flow to the mass flow of the incoming, resulting gas jet is thus achieved. The quantities of the injection and the purity of the oxygen jet into which it is injected, or in which its raceway is injected, are chosen so that the resulting gas jet is still technically pure oxygen.

Coal is fed, for example, as coal dust. Oil is supplied, for example, finely atomized.

The internal gas is preferably preheated to the temperature of the oxygen stream. In the case of natural gas, in the process of pig iron production to which the oxygen contributes, the reducing gas or export gas formed is to be understood. 15 201009394

The data mass flow, volume flow, temperature, pressure of the oxygen jet, as well as the values for mass flow, volume flow, temperature, pressure of the oxygen jet refer to the point of supply of the oxygen jet in the bed.

Brief description of the drawings

Short description of the embodiments

FIGS. 1 to 3 show, on the basis of diagrams, the effects achieved according to the invention.

Figures 4, 5 and 6 show by way of example and schematically how the temperature of the oxygen jet can be increased at a constant flow rate.

FIG. 1 shows an example of an increase in the ratio of the volume flow to the mass flow of an oxygen jet as the penetration depth of the oxygen jet increases. The mass flow is constant.

Figure 1 shows, for example, that increases in the ratio of volume flow to mass flow of about 90% of just 0.22 to just 0.42 m3 / kg, the penetration depth of the oxygen jet by almost 15%. This applies to both flow rates shown.

FIG. 2 also shows an example of the fact that the penetration depth of an oxygen jet into the bed of a melter gasifier increases when the ratio of the volume flow to the mass flow of the oxygen jet is increased.

The mass flow of the oxygen jet is constant. So that at elevated temperature of the oxygen jet, the flow rate remains the same, at higher temperatures larger diameter of the oxygen nozzles - abbreviated to Nozzledia - used in the figure. From the figure 2 * It can be seen that with constant mass flow and constant flow velocity, the penetration depth increases with increasing temperature. As rising temperature over decreasing density means larger volume, there is an increasing penetration depth with increase of the ratio volumetric flow to mass flow of the oxygen jet.

FIG. 3 shows that the ratio of volume flow to mass flow of an oxygen jet increases with decreasing inlet pressure or with increasing temperature.

The basis for the presented figures were a mass flow of 2200 Nm3 / h of pure oxygen, and an absolute pressure at the outlet of the oxygen from the oxygen nozzle of 5.5 or 4.5 bar.

Figures 4, 5 and 6 show by way of example and schematically how the temperature of the oxygen jet can be increased at a constant flow rate. In this case, an oxygen nozzle is schematically indicated in each case on the right edge of the image.

Figure 4 shows schematically how oxygen 1 is heated by a gaseous fuel - in this case from the process for producing pig iron, in which the pig iron is used, resulting Topgas 2 from a reduction shaft, not shown - with a portion of the oxygen 1 in one Burner 3 is burned, and the hot gas obtained during combustion with the unburned oxygen 1 is mixed. The mixing takes place in this case in the combustion chamber 4 of the burner 3, in order to minimize the influence of temperature on the lining of the oxygen-carrying lines. The pressure of • 201009394 17

Oxygen beam remains the same, only the temperature rises.

FIG. 5 shows schematically how oxygen 1 is heated by using indirect heat exchangers 5. In the indirect heat exchanger 5, heat is transferred from vapor 6 to the oxygen, the pressure of the oxygen jet remaining the same.

FIG. 6 shows schematically how a heating of oxygen 1 takes place in two stages. First, a preheating at low pressure of the oxygen jet by means of an indirect heat exchanger 5 and 6 steam is made, and then there is an adiabatic compression of the thus preheated oxygen in a compressor 7. Here, the preheating of the oxygen jet by adiabatic relaxation in a relaxation device 8 of a Initial pressure relaxed to an intermediate pressure, wherein the temperature of the oxygen jet decreases. After the subsequent preheating of the intermediate pressure oxygen is then brought back to the initial pressure in the adiabatic compression and thereby heated to the desired temperature. 18 * 18 * 201009394

List of reference numbers

Oxygen 1 Topgas 2 Burner 3 Combustion chamber 4 Heat exchanger 5 Steam 6 Compressor 7 Relaxation device 8

Claims (9)

Claims 1. A method for increasing the penetration depth of a volumetric flow and a mass flow into the bed of a pig iron production unit, preferably a smelting reduction unit / melter gasifier, or an oxygen-blowing blast furnace, entering oxygen jet of technically pure oxygen for the gasification of existing carbon in the bed f carrier, characterized in that the ratio volumetric flow to mass flow of the oxygen jet is increased. 2. The method according to claim 1, characterized in that is increased at a constant mass flow of the volume flow. 3. The method according to any one of claims 1 to 2, wherein the oxygen jet enters the bed at a flow rate, characterized in that the temperature of the oxygen jet is increased. 4. The method according to claim 3, characterized in that the temperature of the oxygen jet is increased at a constant flow rate. 5. The method according to any one of claims 3 to 4, characterized in that the temperature of the oxygen jet is increased in combination by means of one or more of the following methods: - combustion of a solid, liquid or gaseous fuel with oxygen through a burner, and mixing the resulting hot gas with the oxygen, 20 201009394 - mixing of oxygen with steam and / or hot nitrogen in the mixing chamber or at the Einblasstelle, - use of indirect heat exchangers, - preheating of oxygen by means of a plasma torch and mixing with not so preheated oxygen. 6. The method according to any one of claims 1 to 5, wherein the oxygen jet enters the bed at an inlet pressure, characterized in that the inlet pressure is reduced at a constant mass flow. 7. The method according to any one of claims 1 to 6, characterized in that the temperature of the oxygen jet entering the bed is at least 200 ° C, preferably at least 250 ° C. 8. The method according to any one of claims 1 to 7, characterized in that the flow rate of the oxygen jet entering the bed in the range 100 m / s to the speed of sound, preferably in the range 150 - 300 m / s. 9. The method according to any one of claims 1 to 8, characterized in that together with the oxygen jet an injection of carbon carriers in solid or liquid or gaseous form, in the oxygen jet before, formed in the region of the entry of the oxygen jet into the bed, Race way and / or done in the race way.